Strawberry witches broom

Strawberry witches broom is a severe plant disease caused by phytoplasmas, specifically associated with the Candidatus Phytoplasma fragariae group. These pathogens are specialized bacteria that colonize the phloem of the host plant, severely disrupting nutrient transport and hormonal balance.

The primary hosts are cultivated strawberry plants (Fragaria × ananassa). Once a plant is infected, the pathogen spreads systemically throughout the root system and crown, making the infection permanent and incurable for the individual plant.

Symptoms are distinct and easily recognizable: the plant displays stunted growth, proliferation of small, yellowish leaves, and shortened petioles, which creates a dense, broom-like cluster. Flowering is typically inhibited, or the few berries that form are deformed, hard, and lack commercial or nutritional value.

Transmission occurs primarily through insect vectors, most notably leafhoppers (Cicadellidae), which acquire the phytoplasma by feeding on infected plants and then transmit it to healthy ones. The prevalence of the disease is highly correlated with the population density of these insect vectors in the field.

Management of strawberry witches broom requires an integrated approach because there is no direct chemical cure for infected plants. Key prevention and control strategies include:

• Strict rogueing: immediately digging up and destroying any symptomatic plants.
• Vector control: systematic use of insecticides to manage populations of leafhoppers and other sap-sucking insects.
• Use of certified, disease-free planting material from reputable nurseries.
• Maintaining field sanitation by controlling weeds that act as alternative host reservoirs for phytoplasmas.